The present invention relates to a printing head of an ink-jet printer, more particularly, to an improved printing head of the on-demand type ink-jet printer. In conjunction with color ink jet printers that execute printing of multi-colored figures and characters, one of the prior arts proposes an on-demand type ink-jet printer which prints multi-colored figures and characters using four colors of internally stored ink, yellow, magenta, cyan, and black.
However, the on-demand type color ink jet printers available today still have a problem to solve in their constitution related to the conduction part connected to the orifice. Actually, when driving the printing head at high velocity, ink flowing through the conduction part is accelerated, and eventually overflows from the orifice due to the intense acceleration force.